Linac Based Stereotactic Radiosurgery of Residual Pituitary Adenomas

M. Malacek, J. Steno, M. Sramka, A. Durkovsky, L. Trejbalova

Departments of Neurosurgery and Endocrinology,
Departments of Stereotactic Radiosurgery and Radiology,
Derers Faculty Hospital, Comenius University, Bratislava, Slovak Republic

 

Introduction. Preservation of at least partial pituitary function (PF) is in spite of selective adenomectomy expected to be not always possible. If it is successful and control examinations (endocrinological, MRI) show residual tumor tissue, another risk while trying to preserve a postsurgical PF is the dose of irradiation, which can be harmful to it.

The goals of present study were:
1. to assess a tumor control
2. to asses a PF after radiosurgical irradiation.

The authors undertook a retrospective analysis of tumor control in 16 patients harboring endocrine-inactive pituitary adenoma (PA) and preservation of at least partial postsurgical PF following LINAC-based Stereotactic Radiosurgery (LSRS) in 17 patients harboring various type of PA.

Material and Methods. From May 1992 to April 2004 (12 years), 49 patients harboring residual PA after a previous transsphenoidal or transcranial surgery were radiosurgicaly treated. The mean prescription dose in 16 patients harboring endocrine-inactive PA was 16 Gy (range12 - 20 Gy) and their mean follow-up was 55.3 months = near 4.5 years (range 2 - 130 monhs). The mean presription dose in 17 patients with postsurgical preserved PF was 18.53 Gy (range 14 - 28 Gy) and their mean follow-up was 44.4 months = near 3.7 years (range 3 - 131 months). During the physical examinations of the patients, neuroradiological changes of the residual tumor as well as a PF and a vision were observed.

Results. The study showed the residual tumor control is high (97.96 % out of all 49 patients). No worsening of the vision field as well as no deterioration of PF was found during the follow-up periods of the both patients groups near 4.5 and 3.7 years respectively. The results of LSRS in 16 patients (1 patient died 56 months after radiosurgery from cerebral ischemic stroke with sever right hemiparesis - her autopsy was not done) with postsurgical preserved PF should be considered as preliminary, because a gradual deterioration of it can occur many years (as late as 10 years ?) after the radiosurgery. The irradiation of optical nerves in all 49 patients did not exceed 8 Gy and the dose to brainstem was up to 12 Gy.

Conclusion. LSRS itself seems to be relatively safe and minimally invasive supplemental therapy, which is taken into account by the neurosurgeon during a pituitary surgery, so that the patient is not exposed to unnecessary risk in effort to reach radicality. The tumor control is excelent and no worsening of the vision field as well as no deterioration of postsurgical preserved PF was found during the follow-up periods both patients groups near 4.5 and 3.7 years respectively (the incidence of delayed deterioration of anterior pituitary lobe function in two patients with the preserved PF is still none). However, the reported follow-up of PF after LSRS in many patients is still short - this data require further follow-up.